From Dana Krempel’s
article about rabbit diet:
Fresh, moist greens are about as important as hay in maintaining a healthy intestine. Try broccoli, dark leaf lettuces, kale, parsley, carrots (with tops!), endive, escarole, dill, basil, mint, cilantro, cilantro, spinach, tomato, celery (cut up into 1″ pieces, to avoid problems with the tough strings getting stuck on the molars!). Almost any green, leafy vegetable that’s good for you (including fresh-grown garden herbs such as tarragon and various mints, with the exception of Pennyroyal) are good for a rabbit. Experiment and see which types your rabbit likes best! Rabbits love fresh, fragrant herbs fresh from the garden.
From Brably Hedge’s rabbit care packet:
Celery (leaves are good) – cut celery into small pieces to prevent choking on strings
From carrotcafe:
Celery and rhubarb stalks contain strings that should be removed before feeding. Alternatively, cut the stalks into small pieces.